Since liquid-crystal display devices have a thin profile, a light weight, and low power consumption, they are widely used as display apparatuses such as televisions, personal computers, and PDAs. Recently, large-size liquid-crystal display devices have rapidly been introduced in various fields, such as liquid-crystal display devices for televisions. Such large-size devices suitably employ a multi-domain vertical alignment (MVA) mode because the MVA-mode display devices can be produced at a high yield despite their large areas and can have a wide viewing angle. With the multi-domain vertical alignment mode, the liquid crystal molecules are aligned orthogonally to the substrate surface when no voltage is applied to the inside of the liquid crystal layer. Thus, this mode can provide a higher contrast ratio than the conventional twisted nematic (TN) mode.
In the MVA mode, the tilting direction of the liquid crystal molecules is controlled not by an alignment film but by the protrusions (ribs) formed of an insulating material. The alignment film thus requires no alignment treatment, eliminating static electricity and dust due to an alignment treatment such as rubbing. This removes a requirement for washing or the like treatment after the alignment treatment. Further, the liquid crystal molecules suffer less initial tilting variations. Therefore, this mode is effective to simplify the process, to increase the yield, and to reduce the cost.
Although the MVA mode requires no alignment treatment, it still requires formation of a base film which corresponds to an alignment film. In order to prevent the influences on the alignment of liquid crystal molecules due to an uneven film thickness of this base film or due to contamination by foreign material, and in order to prevent an increase in the number of steps or in the investment in plant and equipment for the formation of a base film, it is more preferable not to form the base film itself.
In recent years, one technique has been focused on in which a liquid crystal composition containing a liquid crystal material in admixture with any polymerizable components such as monomers and oligomers (hereinafter, abbreviated as monomers) is injected into between the substrates, and then heat or light (e.g., ultraviolet radiation) is applied to the composition to polymerize the monomers, thereby forming a polymer layer (PSA layer) (for example, see Patent Literature 1). Such a polymer layer makes it possible to maintain the alignment of liquid crystal molecules even without an alignment film.